The Implementation Of Experimental Platform And Algorithm Design On Networked Control Systems

A great deal of attention has recently been focused on the networked control systems (NCSs) which are based on communication network. With the spread and application of the field bus control system, networked control systems have being given rise to the engineers' concern. Compared with the traditional point to point control systems, networked control systems which are framed on field bus have a lot of advantages such as high reliability, little system wiring, flexible configuration, open communication protocol, realizable information resource sharing, etc. However, the control systems communicate in serial digital line, causing nodes competing for network resources by protocol. Then some uncertainty from network environment will be brought into the control systems inevitably. The key to networked control systems analysis and design will be how to handle the issue caused by network time delay in network environment. Essentially, networked control is an application technology. That's why network control algorithm design should be established in modification and complement of originally developed control algorithm to adapt to the network environment. Accordingly, this paper investigates the control system theory on data network, develops Ethernet Networked Motion Control Open Platform (ENMCOP), establishes methodology on control system design based on network and gets validation on practical experiment of networked control systems.The main contributions in the paper are as following:1. Investigating time delay composition and production mechanism in network environment, the thesis points out loop delay is the focus of network control system design. Extensive discussion is given on the similarity and difference between networked control and traditional computer sample control while loop delay have characteristics as single sample period and multiple sample periods, then qualitative conclusion is drawn that in single sample periodmode NCSs act almost the same as the computer sample control systems; otherwise, in the case of multiple sample periods network delay, multi-frequency switch of sample periods is the important factor causing unstable of the network control systems.2. Considering the significant practical meaning of experimental platform for network control system research, the author implements an Ethernet Networked Motion Control Open Platform, which includes a speed servo motor driver as a net node with embedded Ethernet interface using digital signal processor; a network controller based on PC which is convenient for realizing sorts of control algorithm; network flow disturbers, helping control on network congestion; a visual graphical monitor system on real time network data, displaying control system state curve dynamically. This experimental platform exhibits real problems on network system, and offers a nice experimental environment for network control theoretical research.3. To fix the problem of multiple sample periods during data transfer in network control systems, the paper puts forward a proposal that presumes network time delay and calculates a set of selectable control output sequences without changing the current model based pole assignment control scheme, attaches data selector to the actuator, selects corresponding control output as per real loop time delay. Compared with PID applied in network congestion experiment in different environment, this control algorithm can help to solve the network uncertain time delay problem to a certain extent.4. With deep understanding on data update process of network control system, the thesis brings forward an improved algorithm of networked model predictive control, takes advantage of scroll optimization in control horizon to get optimized control sequences matrix and to improve system control effect while network being congested, which solves multiple sample periods time delay problem of network in a better way. Also, this has been demonstrated byexperimental results in the ENMCOP.5. The relationship between the networked control systems and the industrial IT is illustrated, and the idea is provided to construct virtual loop in the industry control system design based on the network data transfer. A design pattern of complex networked control systems using multi-agent-system model is proposed and the task scheduling problem is resolved based on the contract net technology.Finally, a summary is made on some remaining challenges and research emphases in the next phase.